1. Field of the Invention
The present invention relates to a forming tool for carrying out a bending process on a plate-shaped workpiece, or, more precisely stated, to a tool which forms a workpiece into the form of an arc.
2. Description of the Prior Art
Bending presses, bending rolls, ring formers and the like are commonly known as devices which form a plate-shaped workpiece into an arc by bending. Generally, in a fabricating machine, a fabricating section of which the cross-sectional shape is in the form of an arc is used as a bending tool, and the workpiece is inserted between this tool and an opposing tool. The arc-shaped tool is then pressed against the workpiece to carry out the bending process.
In the case where the workpiece is processed by bending into the shape of an arc, there is always a large amount of deviation after the actual bending process is carried out because there is a variation in the elastic displacement volume of the workpiece after the bending process (usually referred to as spring back volume), depending on the type of work piece and processing conditions, even though the radius of the arc-shaped part of the opposing tool is identical to the bending radius of the workpiece after fabrication.
Accordingly, in the case where the bending radius of the workpiece varies, the actual bending radius must be reportedly measured while repeating the bending process, and it is necessary to select and mount an arc-shaped tool of the desired radius to revise the bending radius every time.
That is, it is necessary to manufacture multiple varieties of arc-shaped tools because of the variation in the bending radius when fabricating the workpiece.
Accordingly, in a conventional bending tool, it is necessary that a larger number of upper tools, each having a different radius for the arc-shaped part of the fabricating section, be assembled as a set, and a large storage area is required to store the upper tools when they are not being used. In addition, because the upper tool is large and heavy, it is not only dangerous to change, but requires a great deal of effort. A quick change is very difficult to accomplish.